The petroleum industry's ongoing quest for improved processes for the production of high octane gasoline, particularly high road octane gasoline, encompasses the search for processes that can extend the base of feedstocks convertible to high octane gasoline while providing high conversion yields in a safe and cost-effective operation. Since moving from lead additives as octane enhancers, the thrust of the industry's manufacturing program in high octane gasoline has moved increasingly toward the use of octane booster such as tertiary alkyl ethers, including methyl tertiary butyl ether (MTBE) and methyl tertiary amyl ether (TAME). Aromatics also continue as a major source of octane enhancers. As a consequence, much effort is directed toward the improvement of etherification processes for the production of MTBE and TAME and more cost-effective and safer processes for the production of aromatics.
Of the many technical challenges presented to research workers in the field in the effort to improve etherification processes for the production of MTBE and TAME, the management of unreacted methanol from the etherification step is one of the more difficult. Typically, to provide favorable equilibrium conditions, the reaction is carried out employing a slight stoichiometric excess of methanol where a large excess would be more effective. But the recovery and recycle of a large excess of unreacted methanol, dictated by both environmental and cost considerations, represents a substantial economic burden on the process as currently practiced.
Where the production of MTBE and TAME are relatively recent developments in the petroleum industry for the production of high octane gasoline, the production of aromatics for that purpose is a fixture of the industry. Acid catalyzed alkylation of aromatics is a commonplace and technologically mature process for the production of the octane enhancing components of gasoline. Substantial improvements to these well-studied processes by research workers in the field are hard to come by. Nevertheless, the challenge remains, for the changing status of feedstock availability, environmental constraints and cost reduction imperatives impose new requirements that must be met.
In comparatively recent years a new technology has emerged that provides surprising advantages in the conversion of oxygenates, olefins and paraffins to gasoline and aromatics. It has been found that medium pore size shape selective zeolite-type catalyst can be effectively employed to convert methanol to olefins and gasoline and convert olefins and paraffins to aromatics and alkylated aromatics. These processes are described in the following U.S. patents, all of which are incorporated herein in their entirety by reference:
U.S. Pat. Nos. 3,931,349 to Tokuo, 4,404,414 to Penick et al., 4,150,062, 4,211,640 and 4,227,992 to Garwood et al., 3,960,978, 4,021,502 to Plank, Rosinski and Givens. Also, methanol conversion is described in the publication C. O. Chang, Catal. Rev. Sci. Eng., 25,1 (1983), also incorporated herein in its entirety.
It has been determined that the properties that these unique zeolite catalysts exhibit, and the processes developed through their implementation provide, a useful route to resolve many of the aforenoted problems associated with the production of methyl tertiary alkyl ethers, aromatics and alkylation of aromatics as currently employed in the industry to produce octane-enhancing components of gasoline.
Accordingly, it is an object of this invention to provide a new and highly useful integrated process for the production of high octane gasoline. Another object of the present invention is to provide an integrated process for the production of high octane gasoline incorporating etherification without methanol etherification feed recycle or recovery to produce MTBE and TAME.
Yet another object of the present invention is to provide an integrated process for the production of high octane gasoline that incorporates etherification in combination with the zeolite catalyzed conversion of methanol, olefins and paraffins.
Still another object of the present invention is to provide a process for the production of high octane gasoline by the zeolite catalyzed conversion of C.sub.2 + olefins and C.sub.3 + paraffins to aromatics and alkylated aromatics in combination with gasoline.
A further object of the present invention is to provide an integrated process for the production of high octane gasoline which can be readily combined with an unsaturated gas plant typically utilized in conjunction with a fluid catalytic cracking process.